1. _Strategy_ regards the theatre of war, rather than the field of battle. It selects the important points in this theatre, and the lines of communication by which they may be reached; it forms the plan and arranges the general operations of a campaign; but it leaves it to the engineers to overcome material obstacles and to erect new ones; it leaves to logistics the means of supporting armies and of moving them on the chosen lines; and to tactics, the particular dispositions for battle, when the armies have reached the destined points. It is well to keep in mind these distinctions, which may be rendered still more obvious by a few illustrations. The point where several lines of communications either intersect or meet, and the centre of an arc which is occupied by the enemy, are strategic points; but tactics would reject a position equally accessible on all sides, especially with its flanks exposed to attack. Sempronius at Trebbia and Varro at Cannae, so placed their armies that the Carthagenians attacked them, at the same time, in front, on the flanks, and in rear; the Roman consuls were defeated: but the central strategic position of Napoleon at Rivoli was eminently successful. At the battle of Austerlitz the allies had projected a _strategic_ movement to their left, in order to cut off Napoleon's right from Vienna; Weyrother afterwards changed his plans, and executed a corresponding _tactical_ movement. By the former there had been some chance of success, but the latter exposed him to inevitable destruction. The little fort of Koenigsten, from its advantageous position, was more useful to the French, in 1813, than the vast works of Dresden. The little fort of Bard, with its handful of men, was near defeating the operations of Napoleon in 1800, by holding in check his entire army; whereas, on the other hand, the ill-advised lines of Ticino, in 1706, caused an army of 78,000 French to be defeated by only 40,000 men under Prince Eugene of Savoy. War, as has already been said, may be either offensive or defensive. If the attacking army be directed against an entire state, it becomes a war of _invasion_. If only a province, or a military position, or an army, be attacked, it is simply regarded as taking the _initiative_ in offensive movements.